Automotive seat assembly having an integral tear seam

ABSTRACT

An automotive seat assembly is provided with an integrated side impact airbag. The seat assembly comprises a seat cushion and a seat back mounted to the seat cushion. A seat cushion trim cover material covers the seat cushion and a seat back trim a cover material covers the seat back. The seat assembly is characterized by a tear seam integrally formed within a bolster section of the seat back trim cover material. The tear seam defines a frangible line of weakness within the trim cover material wherein the airbag will tear through the tear seam when the airbag is deployed and inflated to a position outside of the seat assembly. The subject invention also includes a manufacturing apparatus for forming the tear seam in the trim cover material. The apparatus comprises a template ( 48 ) supporting the trim cover material ( 28 ). A C-shaped raised ridge ( 50 ) extends upwardly from the template to abut the inside surface of the trim cover material ( 28 ). A welder ( 52 ) is disposed adjacent the outside surface of the trim cover material ( 28 ) such that the trim cover material is wedged between the template ( 48 ) and the welder ( 52 ). The welder is aligned with the raised ridge to form the tear seam within the trim cover material.

This application claims the benefit of Provisional Application No.60/086,204, filed 05/21/98.

TECHNICAL FIELD OF THE INVENTION

The subject invention relates to automotive seat assemblies havingintegral airbags. More precisely, the subject invention relates to thespecific characteristics of the seat assembly which ensure a completeand full deployment of the airbag.

BACKGROUND OF THE INVENTION

Government and automobile industry researches are continuously lookingat ways to make can safer. Airbags are frequently installed within thedash board, armrest, and steering wheel of many vehicles to enhance thesafety of the vehicle. European Patent No. 0 749 872 illustrates onesuch example of an airbag in a dash board and European Patent No. 0 733518 illustrates an example of an airbag disposed within an armrest. Bothof these designs form a weakened deployment seam within the plasticmaterial forming the dashboard and armrest. The deployment seam istypically formed on both an inside and outside of the material. Oncedeficiency with forming the seam on both sides of the material is thatthis creates a noticeable cut or depression in the dashboard andarmrest. As disclosed in the European '872 patent, the seams aretypically formed by inserting a welder into the material itself. Thismethod of forming the seams can significantly reduce the operating lifeof the welder.

The frequent use of airbags has lead to the thought of installingairbags in other locations within the vehicle. One prominent directionis toward installing airbags directly within a vehicle seat. Primarily,the airbags are installed within a side bolster of the seat such thatthey provide better head, neck and side protection for the occupant.These airbags are commonly called side impact airbags. Side impactairbags operate much the same fashion as frontal airbags. A crash sensoris often located in a B-pillar of the vehicle which detects a seriousimpact occurring perpendicular to the side of the vehicle. Asappreciated, there is little clearance between the passenger and theoutside of the vehicle door. Hence, side impact airbags must inflatemuch faster than frontal airbags.

The side impact airbags are frequently concealed within the seat by atrim cover material. The trim cover material is typically made up ofmultiple smaller pieces of material which are sewn together. The airbagsbreak through the sewn seams during deployment. One of the majorconcerns with seat integrated side impact airbags is achievingsuccessful deployment of the airbag through the proper seam in the trimcover each and every time.

One frequent difficulty associated with side impact airbag deployment isthat the airbag deploys through the seam at a wrong angle. This limitsthe amount of protection available to the passenger and may even injurethe passenger. Another problem occurs when the airbag exits through thewrong seam such as through the front or the back of the seat. This mayalso cause additional injury and may not adequately protect thepassenger. In addition, the airbag may not exit the seat at all. In thissituation, the airbag balloons within the trim cover material and neverbreaks the seam.

The deployment problems occur for a number of reasons. The trim covermaterial typically has an elasticity which works against the brakingforce the airbag. In addition the trim cover material is secured to afoam pad by either thin wire rods, hog rings, a hook and loop fastener,or a bonding process. None of these manufacturing methods are strongenough to hold the trim cover material to the foam pad when the airbagis being deployed. The airbag will always follow the path of leastresistance and may detach the trim cover from the foam pad such that theairbag will wander within the trim cover itself.

One solution contemplated by the prior art is to sew straps into thetrim cover and tie the straps to the seat back frame to hold the trimcover material to the foam pad and seat back frame. This solution,however, has a number of deficiencies. Some of the deficiencies are thatthe straps may be difficult to secure to the frame, it would bedifficult to ensure proper attachment and proper taughtness, and thestraps may provide unpredictable deployment characteristics.

Accordingly, it is desirable to create a weakened deployment seam withinthe trim cover material that is the weakest point in the trim cover suchthat the airbag can predictably break through the trim cover materialand fully deploy. The deployment seam must also be strong enough tomaintain its integrity during normal use of the seat.

Some solutions have been contemplated by the prior art such as lasercutting and changing the parameters of the stitching. The laser cuttingis unreliable in that the particular depth needed is difficult touniformly achieve. The laser cutting is also time consuming andexpensive. Changing the parameters of the stitching along the area ofdeployment is also difficult to control and expensive to implement.

Ultrasonic welding is a means of fusing pieces of material together andfor forming cuts or grooves within both sides of a material. One suchexample of ultrasonic welding is shown in French Patent No. 2 665 683which ultrasonically welds thin plastic bags. The known ultrasonicwelders, however, have not been modified and thus are not capable offorming seams within relatively thick multilayered pieces of materialsuch as trim cover materials.

SUMMARY OF THE INVENTION

An automotive seat assembly is provided with an integrated airbag. Theseat assembly comprises a seat cushion and a seat back mounted to theseat cushion. A seat cushion trim cover material covers the seat cushionand a seat back trim cover material covers the seat back. The seatassembly is characterized by a tear seam integrally formed within atleast one of the trim cover materials to define a frangible line ofweakness within the trim material wherein the airbag will tear troughthe tear seam when the airbag is deployed and inflated to a positionoutside of the seat assembly.

Accordingly, the subject invention provides a weakened tear seam withinthe trim cover material which is the weakest point in the trim coversuch that the airbag can predictably and effectively break through thetrim cover material and fully deploy. The tear seam is also strongenough to maintain its integrity during normal use of the seat assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 an exploded perspective view of an automotive seat assemblyincorporating an airbag;

FIG. 2 is a perspective view of the seat indicating a tear seam and theairbag in phantom;

FIG. 3 is a perspective view of the seat with the airbag partiallydeployed;

FIG. 4 is a perspective view of a welder for forming the tear seamwithin the trim cover material;

FIG. 5 is a cross-sectional view of the welder with the trim covermaterial disposed therebetween;

FIG. 6 is a perspective view of an inside surface of the trim covermaterial;

FIG. 7 is an alternative embodiment of a template; and

FIG. 8 is another alternative embodiment of the template.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, an automotive seatassembly is generally shown at 10 in FIGS. 1, 2 and 3. The seat assembly10 comprises a seat cushion 12 and a seat back 14 mounted to the seatcushion 12. The seat assembly 10 has an integrated airbag 16.Preferably, the airbag 16 is a side impact type airbag mounted within abolster section 18 of the seat back 14. As appreciated, the airbag 16may be mounted within any suitable section of the seat back 14 and/orseat cushion 12.

As shown in FIG. 1, the side impact airbag 16 includes an inflator 20which inflates the airbag 16 in response to a signal from a crash sensor(not shown). The crash sensor is typically mounted within a B-pillar ofa vehicle (not shown). The airbag 16 is shown in a compacted conditionand in a completely deployed condition in phantom. In addition, theairbag 16 is shown in a non-deployed position in phantom in FIG. 2 and apartially deployed position in FIG. 3. As appreciated, the airbag 16 isillustrated schematically in FIGS. 2 and 3. The inflator 20 and airbag16 are mounted to a bracket 22 which is welded to the seat back 14.Preferably the airbag 16 has a 30 liter volume capacity which allows theairbag 16 to expand over a large area to protect the passenger. Asappreciated, the side impact airbag 16 may be of any suitable size,design or configuration as is known in the art.

Side impact airbags 16 are frequently concealed within the seat by atrim cover material. Specifically,a seat cushion trim cover material 24covers the seat cushion 12 and a seat back trim cover material 26 coversthe seat back 14 as is known in the art. Referring also to FIG. 5, theseat back 26 and the seat cushion 24 trim cover materials each have anoutside surface 28 and an inside surface 30. The outside surface 28 isalso shown in FIG. 4 and the inside surface 30 is also shown in FIG. 6.Specifically, the trim cover materials 24, 26 comprise an outer seatinglayer 32 which defines the outside surface 28. The outer seating layer32 may be of any suitable material such as fabric, vinyl, leather or acombination thereof. A thin foam sheet 34 and a backing material 36 aremounted to the outer seating layer 32 and define the inside surface 30.As appreciated, the trim cover materials 24, 26 may have a differentstructure without deviating from the scope of the subject invention. Thetrim cover materials 24, 26 comprise a plurality of smaller materialpieces 38 which are sewn together to form a plurality of sewn seams 40.An illustrated example of a material piece 38 is shown in FIGS. 4 and 6.The size and shape of the smaller material pieces 38 are dependent uponthe particular seating design. As appreciated, any size and shape ofmaterial pieces 38 may be part of the subject invention.

As illustrated in FIG. 1, the seat back 14 also includes a seat backframe 42 and the seat cushion 12 similarly includes a seat cushion frame(not shown). In the preferred embodiment, the seat back frame 42supports the airbag 16 with the seat back trim cover material 26covering the seat back frame 42 and the airbag 16.

As best shown in FIGS. 2, 3 and 6, the seat assembly 10 is characterizedby a tear seam 44 integrally formed within at least one of the trimcover materials 24, 26 to define a frangible line of weakness within thetrim cover material 24, 26 wherein the airbag 16 will tear through thetear seam 44 when the airbag 16 is deployed and inflated to a positionoutside of the seat assembly 10. Preferably, the tear seam 44 is agroove like indentation formed within the inside surface 30 of one ofthe trim cover materials 24,26. This creates a hidden seam such that theseat assembly 10 may maintain an aesthetically pleasing appearance.Marking on the outside surface 28 of the trim cover material 24, 26 mayalso be done if desired. The tear seam 44 and/or marking on the outsidesurface 28 could resemble some type of logo or design.

Even more preferably, the tear seam 44 is formed within the seat backtrim cover material 26 such that the side impact airbag 16 may be easilydeployed through the bolster 18. The tear seam 44 is formed within theseat back trim cover material 26 between at least a pair of the sewnseams 40. The frangible line of weakness defined by the tear seam 44 isweaker than the sewn seams 40 such that the tear seam 44 will tearbefore the sewn seams 40.

Referring also to FIG. 5, the tear seam 44 has a substantially V-shapedconfiguration when viewed in cross-section. Specifically, the V-shapedtear seam 44 is formed within the foam sheet 34 and the backing material36. The V-shaped tear seam 44 is only illustrative of one embodiment andthe tear seam 44 may have any suitable cross-section without deviatingfrom the scope of the subject invention.

The tear seam 44 is integrally formed within the inside surface 30 ofthe seat back trim cover material 26 by a novel manufacturing methodwhich is now discussed in detail. For illustrative purposes, only theseat back trim cover material 26 will be discussed. It is appreciatedthat seat cushion trim cover material 24 may also be utilized. Themethod of integrally forming the tear seam 44 within the seat trim covermaterial 26 uses a welder 46 and a template 48 having a raised ridge 50.The method comprising the steps of: placing the inside surface 30 of thetrim cover material 26 over the template 48 such that the inside surface30 of the trim cover material 26 contacts the raised ridge 50; movingthe welder 46 adjacent the outside surface 28 of the trim cover material26 such that the trim cover material 26 is wedged between the template48 and the welder 46; aligning the welder 46 with the raised ridge 50 ofthe template 48; and heating the welder 46 to a predeterminedtemperature to integrally form the tear seam 44 within the insidesurface 30 of the trim cover material 26.

The heating of the welder 46 is further defined by ultrasonicallyheating the trim cover material 26 to at least a partially molten stateto integrally form the tear seam 44. The ultrasonic heating of the trimcover material 26 is created by vibratory energy which is converted toheat through friction. As discussed below, any type of ultrasonic weldermay be used as is known in the art. The heat subsequently melts thedesired portion of the trim cover material 26. When a molten state isreached, the vibration is stopped and pressure is the applied from thewelder 46 onto the trim cover material 26. The pressure is maintaineduntil the trim cover material 26 solidifies, thereby forming the tearseam 44 within the inside surface 30 of the trim cover material 26.

The manufacturing apparatus for performing the method of operation andcreating the tear seam 44 is now discussed in detail with reference toFIGS. 4 through 8. The manufacturing apparatus comprises the template 48for supporting the seat back trim cover material 26. As above, only theseat back trim cover material 26 will be subsequently discussed. Thetemplate 48 may be of any suitable size. Although not specificallyshown, the template 48 is preferably the same size as the piece of trimcover material 26 being welded.

The raised ridge 50 extends upwardly from the template 48 for abutmentwith the inside surface 30 of the trim cover material 26. Hence, thetrim cover material 26 is placed face down over the template 48. Thewelder 46 is disposed adjacent the outside surface 28 of the trim covermaterial 26 such that the trim cover material 26 is wedged between thetemplate 48 and the welder 46. The welder 46 is aligned with the raisedridge 50 to form the tear seam 44 within the trim cover material 26.

The welder 46 is an ultrasonic welder which ultrasonically heats aportion of the trim cover material 26 to a predetermined temperature tointegrally form the tear seam 44. The ultrasonic welder 46 includes apower supply (not shown) and a horn 52. A pneumatically activatedcarriage moves the horn 52 upward and downward and an electroniccontroller (not shown) controls the ultrasonic exposure and clampingtime. The horn 52 is preferably an aluminum slotted tool which has asimilar shape as the raised ridge 50. The electronic controller can varythe exposure time which can form deeper and/or wider tear seams. Thedepth and width of the tear seam 44 will depend upon the type of trimcover material 26 and the type of sewn seam 40 used in the seat assembly10. Certain sewn seams 40 are stronger than others.

The trim cover material 26 is wedged between the horn 52 and the raisedridge 50 of the template 48. For illustrative purposes, the horn 52,trim cover material 26 and template 48 are shown in a spaced apartrelationship in FIG. 4. As appreciated, the horn 52 will move downwarduntil contacting the trim cover material 26. The horn 52 of theultrasonic welder 46 is an acoustic tool that transfers the vibratoryenergy directly to the parts being welded. As discussed above, thevibratory energy is converted to heat through friction which melts thedesired portion of the trim cover material 26. The portion of the trimcover material 26 which is heated is the portion which contacts theraised ridge 50. Specifically, the welder 46 heats the foam sheet 34 andthe backing material 36 to form the tear seam 44.

The raised ridge 50 preferably has a substantially C-shapedconfiguration for creating a C-shaped tear seam 44. As appreciated, whenthe airbag 16 deploys and breaks through the C-shaped tear seam 44, atrim cover flap 54 will be created. This is desirable such that the trimcover material 26 does not completely detach from the seat assembly 10and cause any injury. In other words, the preferred configuration of thetear seam 44 does not allow any portion of the trim cover material 26 todetach from the seat assembly 10.

The horn 52 preferably has a C-shaped configuration to correspond to theC-shaped raised ridge 50. The C-shaped edge may be a continuous edge asshown in FIG. 4 or a multiple of smaller sections as shown in FIG. 7. Inaddition, the raised ridge 50 and horn 52 may have a different shapesuch as a U-shaped configuration as shown in FIG. 8. As appreciated, theportion of the trim cover material 26 that melts and subsequently formsinto the tear seam 44 will correspond to the desired shape of the raisedridge 50 and horn 52.

As shown in FIG. 5 and discussed above, the tear seam 44 has asubstantially V-shaped configuration when viewed in cross-section. Theraised ridge 50 has a substantially triangular shaped configuration whenviewed in cross section for forming the V-shaped tear seam 44. Asappreciated, the raised ridge 50 may have any suitable cross-sectionalconfiguration which will create any suitably shaped tear seam 44.

Many modifications and variations of the present invention are possiblein light of the above teachings. It is, therefore, to be understood thatwithin the scope of the appended claims the invention may be practicedotherwise than as specifically described.

What is claimed is:
 1. A method of integrally forming tear seam (44)within a multilayered seat cover material (24, 26) having at least oneouter layer (32) and at least one inner layer (34, 36) by using anultrasonic welder (46) and a template (48) having a raised ridge (50),said method comprising the steps of; placing the cover material (24, 26)over the template (48) within an inside surface (30) of the inner layer(34, 36) in contact with the raised ridge (50); moving the ultrasonicwelder (46) adjacent an outside surface (28) of the outer layer (32) inalignment with the raised ridge (50) of the template (48) and wedgingthe trim cover material (24, 26) between the ultrasonic welder (46) andthe raised ridge (50); and ultrasonically heating the layer (34, 36)with the ultrasonic welder (46) to form a tear seam (44) having at leastone of the inner layers (34, 36).
 2. A method as set forth in claim 1wherein the ultrasonically heating of the trim cover material (24, 26 isfurther defined as heating the inner layers (34, 36) to at least apartially molten state.
 3. A method as set forth in claim 2 wherein theultrasonic welder (46) wedges the trim cover (24, 26) onto the raisedridge (50) until the trim cover material (24, 26) solidifies.
 4. Amethod as set forth in claim 3 wherein the forming of the tear seam (44)is further defined by forming a substantially V-shaped tear seam (44).5. A method as set forth in claim 4 wherein the forming of the tear seam(44) is further defined by providing a substantially triangular shapedridge (50) for forming the V-shaped tear seam (44).